Format PatternMatchValue

[konstin]

Implement formatting for PatternMatchValue, see #5834

Implement formatting for the value pattern:

match x:
    case "Relevant":
        ...

[dhruvmanila]

This could be delegated directly to the expression formatting. We probably just need to make sure that the comments are handled correctly around the pattern itself which might be handled automatically by the expression formatting itself.

[evanrittenhouse]

@MichaReiser I can take this